1. Field of the Invention
The present invention relates to grippers for disc brakes, notably for use on handling equipment such as travelling bridge cranes, in which the gripping of the disc by the pads is obtained by the action of the springs and the releasing by the electromagnet, the action of the springs and of the electromagnet being transmitted to said pads through two levers assembled with pivots in their middle region in the fashion of a laundry clip, in such a way that the springs acting to separate one end of the clip cause the gripping of the pads on the disc at the other end.
2. Description of the Prior Art
In known devices of this type, the springs are placed inside the electromagnet. The gripping forces necessary are large, several thousands of Newtons, and the specific force of the electromagnets being limited by the saturation of the iron at about 100 N per cm.sup.2 of surface, said electromagnets have necessarily a large surface in the plane perpendicular to the forces. At the same time, it is necessary to keep a sufficient thickness at the electromagnet to guarantee a low enough stroke/spring length ratio and to ensure the housing of the coils; the electromagnet-springs assembly then has a considerable volume. In the known devices, said assembly is either placed outside of the levers, on the side -- this increases the lateral bulk --, or above -- this involves the complication of a second lever system --, or between the levers so that the total lateral bulk of the brake is large since it is represented by the cumulative thicknesses of the two levers (which is large since they must withstand bending) and of the thickness of said assembly.
Now the disc on which these grippers act is mostly mounted on a stub shaft projecting from a reducer.
To avoid causing this shaft to operate under large flexion-torsion stresses during braking, the overhang of the disc is reduced to the minimum so that the space available between the housing of the reducer and the plane of the disc is limited. For this reason, only brakes whose electromagnet assembly is on one side of the levers have been able to be developed: said assembly is then placed on the opposite side to the reducer, generally facing a coupling; this arrangement has resulted in the grippers situated on one side or the other of the disc not being identical, so that a "right" and a "left" exist, which constitutes a difficulty in the manufacture of brakes and the maintenance of the machines.